As is well known, in a case of laser cutting a workpiece such as steel materials, cutting is performed as a laser beam irradiated from a laser oscillator is focused by a condenser lens, a cutting portion is heated, and an assist gas is sprayed from a nozzle so as to surround the laser beam to cover the cutting portion, so that combustion reaction occurs in the cutting portion, or cutting is performed as a metal melted by the laser is blown away.
Various technologies relating to a laser cutting nozzle used in the above laser cutting method have been disclosed to improve the processing efficiency (For example, see Patent Document 1).
FIG. 7 is a longitudinal cross-sectional view showing a laser cutting nozzle 100 in the related art. The laser cutting nozzle 100 is formed symmetrically with respect to an axis O of a nozzle main body 101, and a nozzle hole 102 is formed coaxially with the axis O.
Provided that an upstream side in a flow direction of an assist gas is referred to as a base end side and a downstream side is referred to as a front end side, the nozzle hole 102 has a tapered portion 103 whose diameter gradually decreases from a base end side of the nozzle main body 101 toward an opening 102A of a front end of the nozzle hole 102, a cylinder portion 104 connected to a front end side of the tapered portion 103, and a tapered portion 105 connected to a front end side of the cylinder portion 104 and having a diameter that gradually increases toward the opening 102A.
In addition, the base end side of the nozzle main body 101 is composed of a cylinder portion 108 in which a thread formed thereon for mounting on a laser cutting device is formed, a large-diameter portion 109 is formed on a front end side of the cylinder portion 108, and a tapered portion 110 whose diameter gradually decreases toward the opening 102A is formed on a front end side of the large-diameter portion 109.
By the configuration described above, the laser cutting nozzle 100 can perform the laser cutting efficiently.